The overarching goal of the proposed research is to understand the role that biofilms and the local oral environment play in the physical and/or environmental degradation of dental resin composites and to correlate their effect on secondary decay. Understanding the various modes of materials degradation, correlating them to the local biochemistry, and then assessing their relative contribution towards secondary caries are the primary aims of this proposal. The plan is organized into four Specific Aims with the following core attributes: Significant Problem in Dentistry. There is uncertainty surrounding the role biofilms play in composite materials degradation and the correlation to secondary caries. The successful execution of this research plan will lead not only to the better mechanistic understanding of biologically-enhanced materials degradation, but also to the knowledge that may impact the next generation of dental restorative materials. Strong Team. We have assembled a very strong, interdisciplinary team to address all the major components of this problem. The team consists of the following key individuals, their core skill-set and role on this project: Dr. Ed Swift (Chair Operative Dentistry, UNC) - PI, Dental Materials and Clinical Protocols Dr. J. William Costerton (Dir. Biofilm Research, A-S Res. Inst.) - Microbiologist, Biofilm Characterization Dr. Brian R. Stoner (Sr. Dir. Materials and Electronics, RTI) - Biomaterials Characterization Dr. Jeffrey R. Piascik (Principal Scientist, RTI) - Materials Processing, Mechanical Testing and Analyses Innovative Strategy. This proposal employs cutting edge diagnostic techniques (IBIS/FISH) to characterize biofilm etiology. The IBIS database enables us to determine which bacterial species are present, and the Fluorescence In-Situ Hybridization (FISH) technique enables us to map these microbial communities in relation to the compounds being degraded. Furthermore, the research plan introduces a novel diagnostic technique (EIS-DECAY) which utilizes a specially developed chip for screening multiple composite specimens in situ. The latter technique is used to screen for initial biofilm formation or materials degradation, while the former, more sophisticated one enables detailed spatial resolution and speciation. Organized Approach. The plan focuses on identifying modes of degradation by differentiating between abiological (chemical, thermal) and biological (biofilm-assisted) factors. The progression enables us to first understand the mechanistic failure of composite materials (aims 1, 2) and biological substrates (enamel, dentin in aim 3) independently, both with and without biofilm formation, and then to draw final conclusions as they relate to secondary caries (aim 4). Collaborative Research Environment. Both RTI and Allegheny-Singer Research Institutes have the necessary facilities and expertise to perform the materials preparation and testing outlined herein. UNC has both the clinical expertise and resources to direct and carryout the plan of work. Furthermore, both UNC and RTI have a long history of collaborations, with joint publications and existing research collaborations between the co-Investigators on this Proposal.